We have been investigating structure-function relations of peptide hormones, hormone derivatives and analogues, and related compounds using synthetic organic chemistry, biological assay methods, and biophysical techniques. Special synthetic emphasis is placed on the development of high yield methods for the preparation of labeled (2H, 13C, 19F, etc.) amino acids and amino acid derivatives, on refinement of solid phase synthetic methods, and on development of methods for separating moderate sized peptide diastereoisomers. We are using 1H and 13C nuclear magnetic resonance techniques to study the conformations of peptide hormones and hormone analogues with special emphasis on peptide hormone antagonists (inhibitors). Using labeled hormone analogues and derivatives, we are especially interested in developing NMR methods to study peptide hormone-protein interactions using the neurohypophyseal hormone-neurophysin system from the brain. We also utilize circular dichroism, laser Raman spectroscopy, dialysis, and other physical methods to study peptide conformation and structure. An understanding of the underlying chemical and physical principles associated with the biological functions of peptide hormones is being sought.